Vapor source assembly



MTRO# A. o. Du Bols 3,360,600

VAPOR SOURCE ASSEMBLY Dec. 26; 01,967`

Filed July 13,l 1966 5 Sheets-Sheet 1 l A i ls v urunumlmmwlw- 1% I i 5 lf 1|? I@ INVENTOR.

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VAPOR SOURCE vASSEMBLY Filed July l5, 1966 5 Sheets-Shed, 3

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United States Patent O 3,360,600 VAPOR SOURCE ASSEMBLY Andrew Uakley Du Bois, Berkeley, Calif., assigner, by mesne assignments, to Air Reduction Company, Inu corporated, a corporation of New York Filed July 13, 1966, Ser. No. 564,811 12 Claims. (Cl. 13-31) This invention relates to vapor source assemblies for use in vacuum deposition systems and, more particularly, to such a vapor source assembly in which the vapor source Crucible thereof is rotated at speeds -greater than one gradial acceleration.

Vacuum deposition systems generally involve the condensation of a vapor of one material on a substrate of another material, performed in a high Vacuum Chamber.v The material to be deposited is vaporized at high ternperatures in a suitable vapor source assembly located in the high vacuum chamber. The materials may be of various types, such as metals and dielectrics, and the substrate may be of any of a variety of thicknesses. The process may operate on a substrate comprising a continuously moving film, or the substrate may be of a more discrete form.

In a vacuum deposition system, the vapor source assembly in which the material to be deposited is vaporized generally includes a crucible in which charge material is melted and vaporized. Melting and vaporization energy may be supplied by a high energy electron beam or beams directed into the Crucible and against the surface of the charge material therein. The production of vapor by such means provides good control over the thickness, density, and uniformity of the deposited material and also facilitates efficient utilization of materials.

In a particular type of vacuum deposition system, the Crucible of the vapor source assembly is cylindrical and rotates about its axis, which is horizontally disposed. The reason for rotating the Crucible is twofold. First, centrifugal force Causes an even distribution of the molten charge material about the cylindrical wall of the Crucible to provide a symmetrical vapor beam of even density moving out of the Crucible mouth. Second, although the electron beam or beams may im'pinge upon only a small area of the molten Charge, by rotating the Crucible all of the charge is bombarded by the electron beam or beams with a substantially uniform transfer of energy from the beams throughout the charge. Such a rotating Crucible has particular advantage in coating vertically disposed substrates because the vapor beam flows from the Crucible in a substantially horizontal path. Two or more of such crucibles may be arranged in banks in a deposition system for coating particularly large substrates.

For extended periods of operation, it is necessary to replenish the charge material which is vaporized in the Crucible. In connection with rotating crucibles, a desirable way to supply the replenishing charge material is by utilizing a hollow drive shaft for the Crucible. The hollow interior of the drive shaft constitutes an axial access passage and the replenishing material is fed through a nonrotating guide or conduit extending through the access passage in the drive shaft. To minimize the size of the high vacuum chamber, the Crucible drive shaft may extend through an opening in a wall of the chamber with the driving mechanism for the shaft being located outside the chamber. Since the access passage in the drive shaft communicates with the Crucible in the vacuum chamber, suitable means must be provided for preventing loss of the vacuum in the chamber through the access passage. In addition, the drive shaft must be supported for rotation and must be rotatably driven at some place intermediate its ends. It is generally necessary, therefore, that 3,360,600 Patented Dec. 26, 1967 "ice some sort of lubrication be provided for the rotary supporting and driving means.

A further desirable feature in the rotary Crucible types of vapor source assemblies consists in providing a flow of Coolant to and from the -Crucible for maintaining the Crucible below temperatures at which a chemical reaction between the Crucible material and the molten charge material therein would occur. Since the Crucible is rotating, it is generally necessary that the coolant be carried to the Crucible through passages contained in the drive shaft. Thus, in addition to providing support and lubrication for the drive shaft, it is desirable that provision be made for conducting coolant to and from Coolant passages in the drive shaft.

From the foregoing discussion, it will be apparent that, if lubrication and cooling is to be provided, regions of at least four different pressures will exist along the periphery of the rotating drive shaft. These four dilferent pressures are: the high vacuum at regions contiguous with the high vacuu-m chamber and the hollow interior or access passage of the drive shaft; the pressure of lubricant in the region of driving and supporting elements for the drive shaft (generally at atmospheric pressure); and the inlet and outlet pressures of the coolant in regions where it flows to and from passages in the drive shaft. The extreme differences in pressure existing between these various regions along the periphery of the rotating drive shaft, together with the fact that the shaft is rotating and that wear problems are a consequential result of rotation, combine to make an effective sealing arrangement for such a vapor source assembly diflicult to devise.

Accordingly, it is an object of this invention to provide an improved vapor source assembly in which the vapor source Crucible thereof is rotated at high speed.

Another object of the invention is to provide a vapor source assembly having a rotating crucible and drive shaft therefor, wherein provision is made for maintaining at least one region of fluid pressure at the periphery of the drive shaft, and wherein an effective seal is provided between said region or regions and an access passage extending axially the length of the drive shaft.

Still another object of the invention is to provide a shaft and supporting assembly wherein a plurality of pressure differentials are maintained along the periphery of a rotating drive shaft.

A further object of the invention is to provide a vapor source assembly having a rotating drive shaft for the Crucible and wherein a lubricant chamber is provided for lubricating driving elements for the drive shaft, which chamber is effectively sealed from high vacuum in the vapor deposition chamber.

A still further object of the invention is to provide a vapor source assembly having a rotating Crucible and drive shaft therefor, wherein an access passage extends the length of the drive shaft and communicates with the interior of the Crucible for providing access for feed material, wherein provision is made for maintaining a region of coolant pressure at the periphery of the drive shaft for introducing coolant into passages in the drive shaft, and wherein said region is effectively sealed from the access passage of the drive shaft and from a high vacuum Chamber in which the Crucible is disposed.

Other objects and the various advantages of the nvention will become apparent to those skilled in the art from the following description taken in connection with the accompanying drawings wherein:

FIGURE 1 is an elevational partial section view illustrating a portion of a vapor source assembly constructed in accordance with the invention, and showing the drive shaft in elevation and the support housing and seals in section;

FIGURE 2 is an elevational -partial section view, similar to FIGURE l, of the remaining portion of the assembly of FIGURE l;

FIGURE 3 is a sectional view taken along the line 3 3 of FIGURE 2; and

FIGURE 4 is a schematic full section view of the assembly.

The invention comprises a vapor source assembly for use in a vacuum deposition system. The vacuum deposition system includes a wall 12 at least partially defining a vacuum chamber 13. The wall has an opening 11 therein and the vapor source assembly includes a drive shaft 26 which extends through the opening 11 in the wall 12. A crucible 14 is disposed in the vacuum chamber and is secured to one end of the drive shaft. A housing 47 encloses the drive shaft and is vacuum sealed around the periphery of the opening in the wall of the vacuum chamber. The drive shaft has an access passage 100 extending the length thereof, which provides communication between the interior of the housing and the crucible for feeding evaporant material into the crucible. Means 54, 61, 65, 69, 71 and 84 are provided for supporting the drive shaft for rotation and for driving the drive shaft to rotate the crucible. The drive shaft is provided with first and second coolant passages 27 and 28 therein for conducting coolant to and from the crucible. The coolant passages terminate in first and second orifices 159 and 163, respectively, spaced axially along the periphery of the drive shaft.

Four sealing structures 101, 103, 105 and 107 are provided spaced axially along the drive shaft 26 between the periphery thereof and the housing 47. These sealing structures, together with the housing and the drive shaft, define a lubricant confining chamber enclosing at least a portion of the supporting and rotating means for the drive shaft, and also define inlet and outlet coolant confining chambers 146 and 162. The inlet and outlet coolant confining chambers communicate, respectively, with the first and second orifices 159 and 163 and permit coolant ow through the orifices into and from the first and second coolant passages 27 and 28 in the drive shaft. Coolant and lubricant are confined by the sealing structures 101, 103, 105 and 107 to respective regions along the periphery of the drive shaft 26 between the vacuum cham-ber 13 and the end of the access passage 100.

Those sealing structures 101 and 107 which are adjacent the high vacuum regions (i.e., toward the vacuum chamber, and toward the end of the access passage opposite the crucible) each include a pair of axially spaced seals 109, 111, and 169, 171, respectively, and a vacuum pump 132 and 198, for evacuating the space between the seals in each pair. This insures isolation of the high vacuum in the chamber 13 and the access passage 100 from the lubricant and coolant. The sealing structure 107 disposed between a high vacuum region and the coolant confining chamber 162 may include a further axially spaced seal 167 adjacent the coolant confining chamber and means 201 for draining coolant which passes such seal from the coolant confining chamber. This prevents coolant from entering the evacuated space between the other two seals and possibly damaging the vacuum pump which evacuates such space.

Referring now more particularly to the details of the illustrated apparatus, the vapor source assembly of the invention is shown mounted, in a manner subsequently explained, to extend through an opening 11 of a wall 12 which partially defines a vacuum chamber 13. Vacuum chamber 13 may be evacuated to a relatively high vacuum by means not illustrated and contains the substrate (not shown) upon which vapor is to be deposited. 'Ihe actual configuration of the vacuum chamber may be of any suitable form. For example, the chamber may be rectangular, spherical, cylindrical, etc.

The vapor source assembly illustrated includes a crucible 14 formed by a generally cylindrical wall 16 in which an annular coolant iiow chamber 17 is provided. The crucible includes an open end through which vapor, produced in the crucible, escapes in the form of a stream of vapor. The rim of the open end is surrounded by a lip 18 and the annular chamber 17 extends into the lip. A baiie 19 divides the chamber 17 and extends nearly the full length thereof such that only a small space exists between the end of the bafiie and the inner wall of the passage at the lip 18. Coolant, introduced into the passage 17 in the crucible, in a manner subsequently explained, flows down the interior side of the baflie 19 toward the open end of the crucible, and ows around the baflie through the space between the end of the baffle and the interior wall of the chamber 17 to flow back down the outside of the baffle toward the closed end of the crucible.

The closed end of the crucible is comprised of a back wall 21. The back wall 21 includes an inlet passage 22 and an outlet passage 23 through which coolant is conducted to and from the chamber 17 in the cylindrical crucible wall 16. The back wall 21 has an opening 24 therein, the axis of which is aligned with the axis of the cylindrical crucible. The opening has two sections of different diameters, with the smaller of the two communicating with the interior of the crucible. A drive shaft 26 for r0- tating the crucible is secured in the larger diameter section of opening 24. Drive shaft 26 is hollow, for purposes which will be subsequently explained, and its walls contain a pair of semiannular coolant passages 27 and 28. Passage 27 is for conducting coolant to the crucible and communicates with passage 22 in the end wall 21 of the crucible through an opening 29. Similarly, passage 28 is for the return flow of coolant from the crucible and communicates with passage 23 through an opening 31. An O-ring 32 and a similar annular seal 33 are provided on either side of openings 29 and 31 to prevent leakage of coolant.

Driving connection between the drive shaft 26 and the crucible 14 is effected by means of a key 34. Key 34 fits into a suitable keyway in the drive shaft 26 and is secured to the back wall 21 of the crucible by means of a flange 36 bolted to the back wall of the crucible. The key 34 is held in place in the Iiiange 36 by means of a split ring 37 and a retainer ring 38, the latter being bolted to the tiange 36 in a recess therein.

Evaporant material in the crucible 14 is melted by means of one or more high energy electron beams. These beams are produced by suitable electron beam guns (not shown) and are directed into the crucible 14 to irnpinge upon the evaporant material therein. Centrifugal force will hold the molten evaporant material against the cylindrical wall 16 of the crucible 14 when the crucible is rotated.

The drive shaft 26 for the crucible 14 extends through opening 11 in wall 12, and is supported and journalled in a drive shaft housing 47. Housing 47 enclosw most of the drive shaft and extends through opening 11 and is supported therein by an annular fiange 45 welded to the housing 47. Flange 45 is suitably bolted and vacuum sealed (not shown) over the opening 11 in wall 12. Housing 47 includes a forward cylindrical section 48 to which the liange 45 is welded. An annular front retainer flange 49 is bolted to the end of section 48 which projects into the vacuum chamber 13 and is sealed thereto by means of an O-ring 51. The opposite end of cylindrical section 48 has a rear annular retainer flange 52 bolted thereto over a sealing O-ring 53.

As will be explained in greater detail subsequently, the crucible 14 is rotated within the vacuum chamber 13. In order to maintain the rotating crucible 14 and drive shaft 26, and the non-rotating vacuum chamber wall 12 and drive shaft .housing 47, at the same electrical potential to prevent drain of beam current through ball bearings and gears, electrical connection is made between the crucible 14 and the fiange 45. This is accomplished by means of a brush assembly including a brush 39 in electrical contact with the back wall 21 of the crucible. Brush 39 is secured in a brush holder 41 mounted on a bracket 42 which is bolted to the fiange 45. A spring 43 biases the brush 39 against the back wall 21 of the crucible and is held on the bracket by a bolted spring lholder 44. The electrical lead 45 electrically connects the brush 39 with the bracket 42.

Bearing support for the drive shaft is provided by a pair of spaced ball bearings 54 and 61 inside the 4forward cylindrical section 48 of the housing 47. The outer race of forward ball bearing 54 is fixed to the inner periphery of the cylindrical section 4S against the forward edge of a locating shoulder 56 thereon. The inner race of the forward ball bearing S4 is secured on the outer periphery of the drive shaft 26 and rotates therewith. The inner race is located by a shoulder 58 which extends around the annular periphery of the drive shaft and which cooperates with shoulder 56 to secure bearing 54. The outer race of rear ball bearing 61 is located at the rearward edge of locating shoulder 56. The inner races of the two ball bearings are separated by means of a spacer 63 and a thrust ring 64. An annular bevel gear 65, the purpose of which will be subsequently explained, is mounted on drive shaft 26 between the spacer 63 and the inner race of bearing 54. The bearing 61 is held in place by means of a lock washer 67 and a lock nut `68 threaded on a portion of the outer surface of drive shaft 26.

The drive shaft 26 is driven by means of a bevel gear 69 fixed t-o the end of a power shaft 71. Gear 69 engages the annular bevel gear 65 which is drivingly keyed to the drive shaft 26 by means of a key 72 in keyway 70. Power shaft 71 extends outwardly of housing 47 perpendicular to the axis of drive shaft 26 through a cylindrical power shaft appendage 73, bolted over an opening 74 in the forward section 48 and sealed over the opening by means of an O-ring 76. A retainer cap 77 is bolted to the Opposite end of appendage 73 and is sealed thereto by means of an O-ring 7S. Power shaft 71 is driven by a suitable motor 84 (see FIGURE 4), and is journalled in the appendage 73 by a pair of spaced ball bearings 86 and 87.

The power shaft 71 extends through an opening in the retainer cap 77 and is sealed therein by means of a face seal 79. Face seal 79 comprises a moving ring assembly 81 attached to the power shaft '71 and a fixed ring 82. Fixed ring 82 is attached to an annular rubber seal 95 which is attached in a recess in the retainer cap 77. The seal 95 and the fixed ring 82 are preferabaly glued to each other and the cap 77, and effect a tight seal between the cap and the ring. The interface of the face seal 79 is indicated at 83.

The moving ring assembly 81 of face seal 79 is comprised of a housing ring 70 having a cross section approximating the shape of the letter J. The short leg of the housing ring 70 is secured on the power shaft 71 by an annular rubber boot 75 which is stretched around the power shaft and squeezed between the periphery thereof and the short leg of the housing ring 70. The boot insures that the housing ring rotates with the power shaft and is sealed thereto. One end of the rubber boot 75 flares outwardly and a seal ring 80 is glued thereto. Suitable tabs, not shown, extend from the housing ring into receiving slots, not shown, in seal ring 80 to insure that the seal ring rotates with the power shaft. A coil spring 85 is contained by housing ring 70 between the closed end thereof `and the fiared end of the rubber boot 7S to which seal ring 80 is attached. The coil spring presses seal ring 80 against the fixed ring 82 at the interface 83 to effect .the desired seal.

fied considerably without departing from the spirit of this invention.

The drive shaft housing further includes a rear cylindrical section 88 which contains means for conducting coolant to and from the coolant conducting passages 27 and 28 in the drive shaft 26, as will be explained in greater detail subsequently. Rear cylindrical section 88 is bolted at its forward end through a flange 8S and the retaining flange 52 to the forward cylindrical section 48. An end cap 96 is bolted through an annular seal retainer 93 and an annular retaining fiange 89 to a flange 90 on the rear cylindrical section 88, and is sealed against the seal retainer 93 by means of an O-ring 97'. Suitable O- rings 91 and 92 are provided, at the respective mating surfaces between section S8 and flanges 52 and 89, for sealing purposes. An O-ring seal 94 is provided between retainer 93 and ange 89.

In order to replenish the charge material which is vaporized in the crucible 14, provision is made at the rear of the source assembly for feeding replcnishing material through the hollow interior of the drive shaft 26 to the crucible 14. Thus, the hollow interior of the drive shaft constitutes an access passage to the crucible. The feeder apparatus may take any of a variety of suitable forms an-d will depend, in particular, upon the nature of the replenishing material. in the illustrated embodiment for example, the replenishing material is in wire form and is fed from a supply reel (not shown) by means of a pair of drive rollers 97 mounted to a frame 98 secured to the outside of the end cap 96. The wire is fed through suitable vacuum seals (not shown) into an elongated snout 99 which is cantilevered from the end cap 96 and extends into the hollow interior of the drive shaft substantially the entire length of the access passage 100. Snout 99 may be cooled by providing a coolant fiow therein (not shown), and guides the wire through the hollow drive shaft to the interior of the crucible 14. As mentioned before, other types of feeding apparatus may be provided depending on the material. For example, in the case of feeding a granular material into the crucible, an elongated conduit and means for vibrating the conduit to urge the material therealong could be provided. An arrangement similar to snout 99 may be utilized in order to feed material in the form of a rod or bar into the crucible. Preferably, a shield or similar barrier, not shown, is provided at the crucible end of the access passage 100 to prevent vapor in the crucible from entering the passage and clogging the feed material and parts of the apparatus.

It will be noted that the nature of the hollow drive shaft, which directly communicates with the crucible in the interior of the vacuum chamber 13, means that a high vacuum will exist not only at the forward end or crucible end of the drive shaft but at the rearward end as well. This high vacuum is contained within the drive shaft housing 47 at the rearward end of the drive shaft. As a practical matter, it is necessary to provide lubrication for the bearings supporting the drive shaft 26 and for the gears which are driving the drive shaft. It is also necessary to provide means for establishing a coolant iiow to and from the coolant passages in the drive shaft. It will therefore be appreciated that regions of at least four different pressures will exist along the interface between the moving shaft and the fixed elements which support it. These different pressures will be the high vacuum which exists at each end of the drive shaft, and the pressures of the lubricant, inlet coolant, and outlet coolant. It is therefore necessary that the regions of lubricant and coolant be isolated from the high vacuum existing at each end of the drive shaft, and also be isolated from each other. The nature of the moving interface between the drive shaft and its supporting elements make it difiicult to obtain proper sealing while at the same time keeping the useful life of sealing elements above a practical minimum.

The sealing arrangement provided by the invention confines the various pressure regions effectively and has proved to be a practical arrangement from a life standpoint. Four seal structures are provided spaced along the length of the rotary drive shaft in order to isolate the various pressure regions. These seal structures are a forward seal structure 101, two intermediate seal structures 103 and 105, and a rear seal structure 107. These seal structures are constructed to effect suitable isolation between the various major pressure regions despite the existence of extreme differences in pressure between such regions.

Seal structure 101 comprises a pair of axially spaced annular face seals 109 and 111. Face seal 109 is identical to face seal 79 and comprises a stationary ring 113 and annular rubber seal 114, and a rotating ring assembly 115. Ring assembly 115 is shown in outline only and is identical in construction to ring assembly 81, described previously. A sealing interface between the moving ring assembly 115 and the stationary ring 113 is established at 119. Resistance to axial thrust on ring assembly 115 is provided by a shoulder 116 on shaft 26.

Face seal 111 is of identical construction and comprises a stationary ring 121 and rubber seal 122, and a moving ring assembly 123. The interface of seal 111 is indicated at 127. The space between face seals 109 and 111 and between the inner periphery of the annular retainer ilange 49 and the outer periphery of the drive shaft 26 is evacuated through a passage 129 and hose 131 by a vacuum pump 132 (see FIGURE 4). Evacuation of the space between the two face seals 109 and 111 provides a vacuum barrier to isolate the high vacuum chamber 13 from pressures existing on the opposite side of the seal structure 101.

Seal structure 103 is spaced axially from seal structure 101 on the opposite side of the bearings 54 and 61 and the drive gears 65 and 69 for the drive shaft 26. Seal structures 101 and 103, together with the enclosing Walls of the housing 47 and the outer periphery of the drive shaft, form a lubricant chamber in which a bath of lubricating oil may be established to lubricate the supporting bearings and driving gears for the drive shaft. The lubricant may also be ypermitted to lloW up into appendage 73 in which the power shaft 71 is journalled for lubricating the bearing 86 and 87 therein. Thus, face seal 79 also serves to enclose and dene the lubricant chamber. Oil may be introduced into the chamber through an inlet opening 128 and removed therefrom through an outlet opening 130. The inlet opening 128 and the outlet opening 130 are shown on the same side of housing 47 in FIGURE 2 for clarity, however, they may be disposed on opposite sides of the housing in actual construction and as shown in FIGURE 4 in order to facilitate ow of lubricant through the chamber. The pool of oil serves to cool the various moving parts of the system in the chamber and heat is removed therefrom due to the flow of coolant in the hollow drive shaft.

Seal structure 103 comprises a single face seal identical in construction to the face seals 109 and 111. The face seal of seal structure 103 comprises a fixed ring 133 and annular rubber seal 134 secured to a shoulder 145 which extends inwardly from retainer flange 52. The face seal further comprises an elongated rotating ring assembly 135 secured around the outer periphery of the drive shaft and abutting a shoulder of an annular flange 136 which is xed to the drive shaft 26 by means of a locking ring 141 and a set screw 143. Proper pressure at the interface 139 of the ring 133 and ring assembly 135 is established by adjustment of the locking ring 141.

Seal structure 105, which is spaced axially from seal structure 103 along drive shaft 26, defines (with seal structure 103) a coolant inlet chamber 146 for the coolant flowing through drive shaft 26 to the crucible 14. Seal structure 105 consists of a face seal having a fixed ring 147 secured to the inner side of rear cylindrical section 88. The other element of the face seal is comprised of a moving ring 149 surrounding the periphery of the drive shaft 26 and sealed thereto by means of an O-ring 151.

A retainer ring 153 is held by a suitable shoulder 155 on ring 147. Seal structure is spaced from seal structure 103 on the opposite side of the orifice 159 in the drive shaft 26. Orifice 159 permits fluid communication between the coolant inlet chamber 146 and the inlet passage 27 in the drive shaft 26. A water inlet conduit 161 provides communication through the rear cylindrical section 88 from a suitable pressurized coolant source, not shown. Thus, despite rotation of the drive shaft 26, the orifice 159 will be in constant lluid communication with the water inlet chamber 146.

Seal structure 105 serves as the divider between the coolant inlet chamber and the coolant outlet chamber 162. The coolant outlet chamber communicates with the coolant outlet passage 28 in drive shaft 26 through the orillce 163 in the drive shaft. Coolant is removed from the coolant outlet chamber through the outlet conduit 165 -on rear cylindrical section 88. Coolant withdrawn from the system may be cooled and recirculated by suitable means not shown. Seal structure 105 operates to effectively isolate the pressure differences existing between the inlet and outlet coolant chambers, which pressure differences establish the rate of coolant flow through the drive shaft and Crucible.

The coolant outlet chamber is further defined by the rear seal structure 107. Rear seal structure 107 is comprised of three annular face seals 167, 169, and 171. Face seal 167 is adjacent the coolant outlet chamber and is identical to face seals 79, 109 and 111, comprising a stationary ring 173 and annular rubber seal 174 secured in a recess in the retaining flange 89, and a moving ring assembly 175 secured and sealed to the drive shaft 26. The sealing interface between ring assembly 175 `aud ring 173 is indicated at 179.

Seal structure 107 is further comprised of a pair of annular face seals 169 and 171, as previously mentioned. Seals 169 and 171 have a common central element 181 in the form of a ring surrounding the drive shaft and secured and sealed thereto by means of an O-ring 183. Rings 182 and 184 are secured to oppositely disposed recess of ring 181 against annular rubber seals 186 and 188, respectively. Pressure is exerted on repsective faces of the rings 182 and 184 by means of a pair of seal rings 185 and 187 biased thereagainst by coil springs 189 and 191, respectively. Thus, rings 185 and 1182 form a sealing interface at 193, whereas rings 187 and 184 form a sealing interface at 195. Rings 181, 182 land 184 comprise the rotating portion of the seals 169 and 171, and rings 185 and 187 comprise fixed elements which are secured to the seal retainer 93 and are sealed by O-rings 192 and 194, respectively.

The space between the ring 181 and the seal retainer 93 is evacuated through an evacuation Ipassage 197 in retainer 93 and a vacuum conduit 199 by means of a suitable vacuum pump 198 (see FIGURE 4). The vacuurn thus established helps to isolate the high vacuum region at the rear of the `drive shaft 26 from the coolant outlet chamber 162.

Because of the extremely high pressure differential which exists between the vacuum region between seals 169 and 171 and the water outlet chamber 162, there may be a tendency for coolant to pass from chamber 162 into the said vacuum region. If such coolant were to enter the evacuation passage 197, damage to the vacuum pump 198 might result. In order to prevent this, the two seals 167 and 169 are provided, rather than a single seal. In addition, a drain vent 201 is provided communicating with the space between seals 169 an-d 167 lat the outer periphery of the drive shaft 26. This drain vent 201 is at atmospheric pressure, which pressure will lie between the pressure in the coolant outlet chamber and the pressure in the vacuum region between seals 169 and 171. Accordingly, any seepage of coolant, such as water, past seal 167 will be drained through the drain vent 201 and hence will not enter the passage 197. Such an expedient is generally not required between the high vacuum region and the lubricant chamber because a higher viscosity of the lubricant makes seepage unlikely, and if seepage of the oil did occur it would not be harmful to the pump. A suitable drain vent may be provided at such place, however, if found to be desirable.

The vapor source assembly of the invention stably suspends a rotating watercooled crucible, providing inlet and outlet coolant connections from the static housing to the rotating crucible and providing lubrication to the support bearings and driving gears. The regions of difiering pressures along the interface of the rotating drive shaft for the crucible are effectively isolated from each other and from the high vacuum which exists at each end of the rotary drive shaft. In the event of seal leakage, the vacuum pump out regions provided at each end of the rotary drive shaft between face seals will prevent loss of vacuum in chamber 13. The pressure differentials which may exist along the interface of the shaft are, by way of example, a pressure of about IAO@ yof a micron of mercury absolute at each end of the shaft, a pressure in the guard vacuum regions of about 100 millitorr, a pressure approximating atmospheric pressure at the lubricant chamber, and a pressure of 50 to 100 p.s.i. at the coolant inlet chamber with a coolant pressure drop of about 20 to 30 p.s.i. from the inlet chamber to the outlet chamber The invention provides an assembly in which reliable sealing exists with a variety of fiuids and pressures. The type of sealing elements used, together with their positioning and the general structure of the system provide trouble free operation and the likelihood of seal failure is diminished.

It may therefore be seen that the invention provides an improved vapor source assembly for use in a vacuum deposition system and in which the vapor source crucible thereof is rotated at a high speed. Provision is made for conducting coolant to the crucible and for lubricating the drive shaft therefor. Various modifications and embodiments of the invention other than those illustrated and described herein will become apparent to those skilled in the art from the foregoing descrption. Such other modifications and embodiments are intended to fall within the scope of the appendant claims.

What is claimed is:

1. A shaft and supporting assembly for maintaining a plurality of regions of different pressures at the periphery of a rotating shaft intermediate the ends thereof, which shaft extends between two regions of a relatively high vacuum, said lassembly including in combination: a rotary shaft, a housing enclosing said shaft and adapted for at least partially enclosing the high vacuum regions, a plurality of annular seal means spaced axially along said shaft between the periphery thereof `and said housing, said seal means defining a plurality of pressure confining chambers for maintaining regions of different pressures at the periphery of the shaft, said seal means including first and second seal means positioned to be adjacent, respectively, the two high vacuum regions, said first and second seal means each comprising a pair of axially spaced annular seals and further comprising means for evacuating the space between said axially spaced seals.

2. An assembly in accordance with claim 1 wherein said chambers defined by said seal means are adapted to confining lubricant and coolant for said shaft.

3. An assembly in accordance with claim 1 wherein each of said seal means comprises an annular face seal having a rotary seal ring secured to said shaft and a xed seal ring secured to said housing.

4. A vapor source assembly for use in a vacuum deposition system having a wall Iat least partially defining a vacuum chamber, such wall having an opening therein, said assembly including in combination: a drive shaft for extending through the opening in the wall, a crucible for positioning in the chamber secured to one end of said drive shaft for receiving evaporant material which is electrically heated and vaporized, a housing enclosing said drive shaft and adapted to be secured in the opening in the wall and to be vacuum sealed about the periphery thereof, rotary means in said housing supporting said drive shaft for rotation, means for rotating said drive shaft to rotate said crucible, said drive shaft having an Iaccess passage extending the length thereof and communicating with the crucible for feeding evaporant material to the crucible, said drive shaft having coolant passages therein for conducting coolant to and from said crucible, said drive shaft having a plurality of orifices spaced axially along the periphery of said drive shaft yand communicating with said coolant passages, and first, second, third and fourth annular seal means spaced axially Ialong said drive shaft between the periphery thereof and said housing, said first and second seal means defining a lubricant confining chamber enclosing at least a portion of said rotary means, said second, third and fourth seal means defining input and output coolant confining chambers contiguous with said orifices, whereby coolant and lubricant are confined to respective regions -along the periphery of said drive shaft between the vacuum chamber and the end of said access passage opposite the crucible.

5. A vapor source Iassembly in accordance with claim 4 wherein said first, second, third and fourth seal means are arranged in stated order, and wherein said first and fourth seal means each comprise a pair of axially spaced annular seals and means for evacuating the space between said axially spaced seals.

6. A vapor source assembly in accordance with claim 4 wherein said fourth seal means are disposed adjacent one of said coolant confining chambers and comprise first, second and third axially spaced annular seals disposed in stated order away from said one coolant confining chamber, and means are provided for evacuating the space between said second land third seals, said housing having a passage therein communicating with the space between said first and second seals to provide drainage for coolant passing said first seal from said one coolant confining chamber adjacent thereto.

7. A vapor source assembly for use in a vacuum deposition system having a wall at least partially defining a vacuum chamber, such wall having an opening therein, said assembly including in combination: a drive shaft for extending through the opening in the wall, a crucible for positioning in the chamber secured to one end of said drive shaft for receiving evaporant material which is electrically heated and vaporized, a housing for said drive shaft adapted to be secured in the opening in the wall Iand to be vacuum sealed about the periphery thereof, bearing means in said housing supporting said drive shaft for rotation, gear means coupled to said drive shaft exteriorly of the vacuum chamber and within said housing for rotating said drive shaft to rotate said crucible, means for conducting lubricant to said gear means and said bea-ring means at a pressure exceeding the pressure in the vacuum chamber, first and second seal means between said housing and said drive shaft and axially spaced along said drive shaft, each of said seal means being disposed on a respective side of said gear means and said bearing means to define a lubricant confining chamber therefor, with said first seal means being disposed between said lubricant confining chamber and the vacuum chamber to seal the lubricant confining chamber from communication with the v-acuum chamber.

8. A vapor source assembly in accordance with claim 7 wherein said first seal means comprise a pair of annular face seals axially displaced from each other, and further comprise means for effecting a continuous evacuation of the space between said seals.

9. A vapor source assembly in accordance with claim 7 wherein third and fourth seal means are provided bctween said housing and said drive shaft axially spaced from each other and said second seal means on the opposite sides of said first seal means, said second and third seal means defining a first annular coolant confining chamber and said third and fourth seal means defining a second annular coolant confining chamber, wherein said drive shaft is provided with coolant passages therein communicating with said first and second coolant confining chambers for conducting coolant to and from said crucible, and wherein means are provided for conducting coolant to one of said first and second coolant confining chambers and conducting coolant from the other of said first and second coolant confining chambers.

10. A vapor source assembly for use in a vacuum deposition system having a wall at least partially defining a vacuum chamber, such wall having an opening therein, said assembly including in combination: a drive shaft for extending through the opening in the wall, a crucible for positioning in the chamber secured to one end of said drive shaft for receiving evaporant material which is electrically heated and vaporized, a housing enclosing said dripe shaft and adapted to be secured in the opening in the wall and to be vacuum sealed about the periphery thereof, rotary means in said housing supporting said drive shaft and adapted to be secured in the opening in shaft to rotate said crucible, said drive shaft having an access passage extending the length thereof and communicating with the crucible for feeding evaporant mate- 'rial to the crucible, said drive shaft having a coolant passage therein, said coolant passage terminating in an orice at the periphery of said drive shaft, and first and second seal means spaced axially along said drive shaft between the periphery thereof and said housing, said first and second seal means being positioned on opposite sides of said orifice and defining a coolant chamber to provide continuous fluid communication through said orifice between said passage in said drive shaft and said coolant chamber while said drive shaft is rotating.

11. A vapor source assembly in accordance with claim 10 wherein said second seal means is disposed on the opposite side of said first seal means from the crucible, said second seal means comprising, first, second and third axially spaced annular seals and means for evacuating the space between said second and third seals, said first, second and third seals being disposed in stated order from said coolant confining chamber, said housing having a passage therethrough communicating with the space between said first and second seals to provide drainage for coolant passing said first seal from said coolant confining chamber.

12. A vapor source assembly in accordance with claim 10 wherein said coolant passage is of a generally semiannular cross section and is disposed between said access passage and the periphery of said drive shaft.

No references cited.

MORRIS KAPLAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,360,600 December 26, 1967 Andrew Oakley Du Bois It is hereby certifedjy-that error appears in the above numbered patent requiring correction a'rld that the said Letters Patent should read as corrected below.

Column 5, line 48, for "preferabaly" read preferably column 7, line 42, for "bearing" read bearings column 8, line 4l, for "recess" read recesses column ll, line 20, for "dripe" read drive lines 23 and 24, for "drive shaft and adapted to be secured in the opening in shaft to rotate said Crucible" read drive shaft for rotation,

means for rotating said drive shaft to rotate said Crucible Signed and sealed this 11th day of March 1969.

(SEAL) Attest:

EDWARD I. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A SHAFT AND SUPPORTING ASSEMBLY FOR MAINTAINING A PLURLITY OF REGIONS OF DIFFERENT PRESSURES AT THE PERIPHERY OF A ROTATING SHAFT INTERMEDIATE THE ENDS THEREOF, WHICH SHAFT EXTENDS BETWEEN TWO REGIONS OF A RELATIVELY HIGH VACUUM, SAID ASSEMBLY INCLUDING IN COMBINATION: A ROTARY SHAFT, A HOUSING ENCLOSING SAID SHAFT AND ADAPTED FOR AT LEAST PARTIALLY ENCLOSING THE HIGH VACUUM REGIONS, A PLURALITY OF ANNULAR SEAL MEANS SPACED AXIALLY ALONG, SAID SHAFT BETWEEN THE PERIPHERY THEREOF AND SAID HOUSING, SAID SEAL MEANS DEFINING A PLURLITY OF PRESSURE CONFINING CHAMBERS FOR MAINTAINING REGIONS OF DIFFERENT PRESSURES AT THE PERIPHERY OF THE SHAFT, SAID SEAL MEANS INCLUDING FIRST AND SECOND SEAL MEANS POSITIONED TO BE ADJACENT, RESPECTIVELY, TWO HIGH VACUUM REGIONS, SAID FIRST AND SECOND SEAL MEANS EACH COMPRISING A PAIR OF AXIALY SPACED 